Bandgap voltage reference circuits are useful in a wide variety of circuits, such as audio amplifiers, sense amplifiers for memory circuits, analog references, and the like. These bandgap voltage reference circuits are desirable because they provide a reference voltage that is stable over wide ranges of temperature. Many applications require very low noise operation, especially at low frequencies. However, bipolar transistors used in the bandgap voltage reference circuit introduce significant low-frequency noise. If other low-frequency noise sources are minimized, this contribution will dominate low-frequency noise in the circuit.
In the following description, the use of the same reference numerals in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.